Evaluation of the persistence of three larvicides used to control aedes aegypti in arapiraca, northeastern Brazil

Abstract

The chemical control of the mosquito Aedes aegypti is a great challenge worldwide, since several populations of this species are already resistant to traditional insecticides, such as temephos. In Brazil, alternative larvicides, such as Bacillus thuringiensis israelensis (Bti) and pyriproxyfen, have been used more recently. In this study we evaluated the persistence of pyriproxyfen (Sumilarv 0.5%G), 2 commercial formulations of Bti (Vectobac WDG and Vectobac G), and temephos (Fersol 1G) under field and simulated field conditions with treatments exposed to sun and shadow. In the field tests, the 2 formulations of Bti presented less persistence in the 8th wk of evaluation (46% and 37% positivity) compared with temephos (3.6% and 6.8% positivity) and Sumilarv (6.6% and 3.8% positivity) in containers exposed to the sun and shadow, respectively. In the simulated field trial, temephos and the 2 formulations of Bti presented high persistence (100% mortality at 8th wk) when applied in the water box and in deposits placed in the shade. In containers exposed to the sun, the persistence of these products was lower (.80% mortality by temephos after 4 wk, Bti formulations for 3 wk, and Sumilarv for 6 wk). Based on these data, however, Sumilarv presented better performance in the containers exposed to the sun than the 2 formulations of Bti (Vectobac G and Vectobac WDG), which were affected by the sun.